This relates to imaging systems and, more particularly, to imaging pixels with dummy transistors that reduce reset charge injection.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) may be formed from a two-dimensional array of image sensing pixels. Each pixel receives incident photons (light) and converts the photons into electrical signals. Image sensors are sometimes designed to provide images to electronic devices using a Joint Photographic Experts Group (JPEG) format.
With typical image sensing pixels, capacitive coupling between the gate terminal of a reset transistor and the source-drain terminals of that reset transistor leads to reset charge injection. On the falling edge of a reset clock applied to the gate terminal of the reset transistor, this capacitive coupling pulls down the voltage on the pixel's floating diffusion node. The lowered voltage on the floating diffusion node limits the available voltage swing of the pixel. Because of these effects, the dynamic range of typical image sensing pixels is reduced.
It would therefore be desirable to provide imaging pixels that exhibit reduced reset charge injection effects.